Tube Output (25-75 Watts) Single Ended - HI-FI 1627-1642 Series - Features

Nov 2, 2026

Tube output transformer series documentation for 25–75 watt single-ended HI-FI applications, featuring “over designed” Class-A performance with triode/tetrode/pentode-compatible output circuits. Specifies shielded four-slot chassis type X mounting, insulated flexible leads, and target frequency response of at least 20 Hz to 20 kHz at full rated power. Describes core gap for Class-A saturation reduction, 40% screen tap for versatile ultra-linear operation (except specific models), provided wiring guidance, and replacement guidance for single-ended use.

LanguageEnglish

CategoryTechnology

FormatPDF

Pages2

Reading Time5 min

AccessFree to download

Features

Construction and electrical specifications

Ultra-Linear screen tap and model exceptions

Wiring connections and recommended tube types

Notes and usage guidance

Tube Output (25-75 Watts) Single Ended-HI-FI 1627-1642 Series Features "Over designed" for high fidelity, single ended, Class-A, tube output circuits (triode, tetrode or pentode tubes) . Enclosed (shielded), four slot, chassis Type "X" mounting. Frequency response at [least 20 Hz. to](least 20 Hz. to) [20 Khz. at](20 Khz. at) full rated power (+/-1 db max., ref. 1 Khz.) Insulated flexible leads 8" min. For maximum versatility, all units (except the 1642SE & 1638SEA) include a 40% screen tap for Ultra-Linear, tetrode/pentode operation (if desired) . The 1642SE & 1638SEA do NOT include this screen tap as they were designed principally for high impedance triode tubes. High quality laminations,(M6) grain oriented silicon steel. Core is gapped to reduce core saturation in Class-A tube amplifier circuits. For general purpose or replacement use in single ended tube output circuits see our 125SE Series. | Part No. | Primary | | Ultra
Linear Secondary Hipot Mounting | | | | --- | --- | --- | --- | --- | --- | | | Audio | Impedanc
e Max. DC | 40%
Primary | Impedanc
e Test | Weight Overall Dimensions Slot | | | Watts (Ohms) Bias Tap (Ohms) (VRMS) (lbs.) A B C D E G | | | | | | 1626SEA 25 600 250 ma. Yes 4-8-16 2000 11 3.75 4.44 4.56 3.00 3.31 0.20 x 0.38
1640SEA 30 1250 200 ma. Yes 4-8-16 2000 11 3.75 4.94 4.56 3.00 3.81 0.20 x 0.38 | | | | | | | Part No. | Primary | | Ultra
Linear Secondary Hipot Mounting | | | | --- | --- | --- | --- | --- | --- | | | Audio | Impedanc
e Max. DC | 40%
Primary | Impedanc
e Test | Weight Overall Dimensions Slot | | | Watts (Ohms) Bias Tap (Ohms) (VRMS) (lbs.) A B C D E G | | | | | | 1627SEA 30 2500 160 ma. Yes 4-8-16 2000 11 3.75 4.94 4.56 3.00 3.81 0.20 x 0.38 | | | | | | | 1630SEA 30 3500 135 ma. Yes 4-8-16 2000 11 3.75 4.94 4.56 3.00 3.81 0.20 x 0.38 | | | | | | | 1628SEA 30 5000 120 ma. Yes 4-8-16 2000 11 3.75 4.94 4.56 3.00 3.81 0.20 x 0.38 | | | | | | | 1642SE 75 5000 300 ma. No 4-8-16 3500 28 4.38 7.50 5.25 3.50 5.88 0.20 x 0.38 | | | | | | | 1629SEA 30 6500 100 ma. Yes 4-8-16 2000 11 3.75 4.94 4.56 3.00 3.81 0.20 x 0.38 | | | | | | | 1638SEA 30 10000 90 ma. No 4-8-16 2000 11 3.75 4.94 4.56 3.00 3.81 0.20 x 0.38 | | | | | | RED wire connects to B+ BLUE/YELLOW wire connects to screen (optional use) BLUE wire connects to the tube plate The 1642SE & 1638SEA do not include a primary screen tap (as they are designed for triode applications) . Suggested Tube Types: | Part No. | Triodes | Pentodes | | --- | --- | --- | | 1626SEA | 6C33 | - | | 1640SEA | Parallel-2A3, 6A3, 6B4G, 300B, 572B, 811A | Parallel-6550, 6CA7 | | 1627SEA | 2A3, 6A3, 6B4G, 300B | 6CA7, 6L6, 807, 5881, 6550, Parallel-6AQ5, 6V6, EL84 | | 1630SEA | 2A3, 6A3, 6B4G, 300B | 6CA7, 6L6, 807, 5881, 6550, Parallel-6AQ5, 6V6, EL84 | | 1628SEA | 211, 300B, 572B, 811A | 6AQ5, 6V6, 6L6, 807, 5881, 6550, EL84 | | 1642SE | Parallel-211, 572, 811A, 845 | - | | 1629SEA | 211, 811A, 572B, 845 | 6AQ5, 6V6, 6L6, 807, 5881, 6550, EL84 | | 1638SEA | 211, 845 | - | Notes: The above examples of possible combinations are to help you narrow down the choices of transformers for your favorite tube types. How you operate the tubes (ultra-linear, bias, plate voltage, operating points, etc.) will change optimum plate load impedance. Only a few of the most popular tubes are shown. A tube manual or tube manufacturer's technical data sheets should be consulted first, before making a decision on a proper output transformer. Tags: audio transformer , tube output , single ended , hi-fi , shielded , triode , tetrode , pentode Data subject to change without notice. © 2026. Hammond Manufacturing Ltd. All rights reserved.

FAQs

What transformer mounting and shielding design is used in the 1627-1642 series?

The series uses an enclosed (shielded), four-slot chassis with type X mounting and insulated flexible leads for connection.

Do all models include a 40% screen tap for ultra-linear operation?

Most units (except the 1642SE & 1638SEA) include a 40% screen tap for ultra-linear, tetrode/pentode operation if desired. The 1642SE & 1638SEA exclude this tap because they are designed mainly for high-impedance triode use.

How does the core design support Class-A tube amplifier operation?

The core is gapped to reduce core saturation in Class-A tube amplifier circuits, helping maintain performance under Class-A conditions.

Nov 2, 2026

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